The industrial world is facing a tremendous problem in the disposal of the waste that is being generated by industry. The Environmental Protection Agency has issued regulations on the disposal of such waste, and industry is struggling with developing an economical method for the disposal of waste which also meets the requirements of such regulations.
Incineration has been used in the past as a means for the disposal of waste. See the article "Circulating Bed Incineration of Hazardous Wastes" by Dickinson, Holder, and Young published in CEP, Mar. 1985.Prior art incineration is a very costly process requiring highly sophisticated incineration equipment. Oftentimes, such incineration processes result in the formation of other undesirable contaminants which cannot be emitted to the environment.
Hydrocarbon waste is one of the wastes for which there is a disposal problem. Examples of hydrocarbon wastes include alkaryls, dioxin, fluorinated hydrocarbons, toluene, polychlorinated biphenyls (PCBs), mineral oil contaminated with PCBs, chlorinated phenols, various pesticides and herbicides, contaminated soils, absorbents such as carbon black, and other wastes having hydrocarbons. Hydrocarbon waste is primarily gaseous and/or liquid. However, these gaseous and/or liquid hydrocarbon wastes may also include entrained solids. Attempts have been made to burn such hydrocarbon wastes. However, the flue gases emitted from such prior art waste furnaces must meet the requirements of the Environmental Protection Agency. The EPA requires that the resulting airstream of flue gases be practically 100% free of contaminants. Prior art systems have had difficulty achieving a complete combustion of hydrocarbon waste so as to meet these EPA requirements. See the article entitled "Hazardous Waste Management New Rules Are Changing the Game" by Donald R. Cannon published in Chemical Week, Aug. 20, 1986.
Prior art waste combustion systems generally operate under a negative pressure (below atmospheric) where the pressure in the combustion chamber is, for example, a fraction of an inch of water column of vacuum. The prior art combustion chamber is not pressurized to insure there are no leaks of the waste from the combustion chamber into the atmosphere. The prior art waste combustion systems, therefore, require a combustion chamber which is excessive in size. Further, the particles of waste float in the combustion chamber as they are burned. This procedure requires that the combustion process be operated over a longer period of time to insure complete combustion of the waste.
One such prior art system is operated by the Rollins Company where liquid waste and air are mixed for initial combustion in a lodby for emission into an afterburner chamber for more complete combustion. A rotary kiln is used for the combustion of solid waste which is also emitted into the afterburner chamber. Air is introduced into the afterburner chamber to move and rotate the waste for more complete combustion. A vacuum is placed on the afterburner chamber by an air blower to move the combustion products from the afterburner to a water scrub. After the water scrub, the effluent passes to a bag house. This prior art system is large and very expensive. The afterburner alone could be of the size 40 feet by 60 feet and 10 feet high.
U.S. Pat. No. 4,120,639 to Thekdi, et al discloses a high momentum industrial gas burner designed to create a high velocity. The various chambers of the burner are designed so that the fluid pressure within the burner is less than atmospheric pressure. An air and fuel housing is mounted to a block of combustion chambers. The gas fuel flows through a nozzle into a first chamber, and air from an air chamber flows through an annular orifice into he first chamber to be mixed with the fuel and ignited. The combustion products enter a larger diameter chamber to recirculate the gases and the flame. The combustion products from this chamber enter a flame tunnel having a smaller diameter. The block design includes a chamber where the combustion products flow from a larger diameter chamber into a narrower chamber.
U.S. Pat. No. 3,485,566 to Schoppe discloses a combustion gas chamber comprising a burner head mounted on a conical-shaped flame tube. The flame tube widens conically in the direction of the main flow of the throughput. The fuel can be fed in at the intake end where the combustion air is also fed in via an air swirling device with predominately radially directed guide vanes and with an accelerating nozzle for the flame gases connected with the outlet end of the flame tube.
U.S. Pat. No. 3,663,153 to Bagge and Kear discloses a combustion device for gaseous fuel having a coaxial burner opening into a combustion chamber. The flame chamber has a smaller diameter than the combustion chamber, and the combustion chamber has a mixing throat which widens and then narrows.
Also of interest are U.S. Pat. Nos. 4,309,165; 4,410,308 and 4,556,386 to McElroy which disclose an air/fuel control system and preheated combustion air. The combustion air is pressurized to create flue gas velocities sufficient to cause a back pressure within the combustion chamber. U.S. Pat. No. 3,880,571 to Koppang, et al discloses a burner assembly for providing reduced emission for air pollutants. U.S. Pat. No. 3,644,076 to Bagge discloses a liquid fuel burner.
The present invention provides a multi-stage combustion process which insures complete waste combustion. Further, the system of the present invention pressurizes the waste and oxygen supply to shorten the period of time for achieving waste combustion to thereby more efficiently and economically dispose of such waste. The present invention also permits a smaller combustion chamber. In addition the multi-stage combustion system may include a heat exchanger for recovery of heat formed in the combustion of the waste. Thus, the present invention overcomes defects in the prior art.